This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled Transformer for a Microwave Oven earlier filed in the Korean Industrial Property Office on Jul. 26, 1999, and there duly assigned Serial No. 99-30303 by that Office.
1. Field of the Invention
The present invention relates to a transformer for a microwave oven, and more a particularly to a transformer for a microwave oven having an improved insulating structure for a coil.
2. Description of the Related Art
Generally, a transformer for a microwave oven receives a particular commonly used voltage and outputs a high voltage for driving a magnetron. A magnetron is an electron tube in which the flow of electrons from the cathode to one or more anodes is controlled by an externally applied magnetic field. The magnetron is used to generate alternating currents at microwave frequencies. The magnetron is used in a microwave oven for producing microwaves for use in cooking food.
A transformer is an electrical device through electromagnetic induction transforms electric energy from one or more circuits to one or more-other circuits at the same frequency, but usually at a different voltage and current value. The transformer includes at least two coils. The transformer changes voltage in direct proportion to the ratio of the number of turns of its primary and secondary windings. A core is placed within the coils to intensify the magnetic field.
The cores and coils are insulated by an insulating paper. The insulating paper can be damaged by humidity or shock. Varnish impregnation may be performed on the transformer to prevent vibration between the cores and the coils through magnetic field changes, to improve the heat release characteristics, and to avoid dirt, humidity and foreign substances. The manufacturing cost is increased by varnish impregnation because of time needed for the process. Manufacturing time is further increased by a processes of removing varnish from areas of the transformers that cannot have the varnish. When using a vacuum impregnating method for varnish impregnation, the degree of varnish impregnation varies greatly causing possible defects. In a microwave oven, since vibration occurs at the iron plates of a transformer, the plates have to be firmly secured.
Exemplars of the art U.S. Pat. No. 5,660,756 for High-voltage Transformer for a Microwave Oven Power Supply issued to Calmettes et al., U.S. Pat. No. 4,858,095 for Magnetron Drive Apparatus issued to Narita et al., U.S. Pat. No. 4,885,445 for High-frequency Transformer for Microwave Oven issued to Taniguchi, U.S. Pat. No. 4,886,951 for Power Supply for a Magnetron Having a Rectifying Circuit, Switching Circuit, and Transformer issued to Matsumoto et al., U.S. Pat. No. 5,025,489 for Transformer Having Shielding Wall for Driving a Magnetron issued to Yamaguchi, U.S. Pat. No. 5,954,988 for High Voltage Transformer of a Microwave Oven Having a Structure for Radiating Heat issued to Lee, and U.S. Pat. No. 5,973,307 for High Voltage Transformer with Side Insulation Support and Formed with Through-holes for Lead Wires issued to Cho disclose transformers for microwave ovens.
I have found that the background art does not show a transformer for a microwave oven that has protection from internal and external shock, foreign substances, heat, while also reducing the cost of manufacture.
Accordingly, an object of the present invention is to provide a transformer for a microwave oven capable of preventing quality deterioration of the transformer which is caused by damaged insulating paper.
It is another object to provide a transformer for a microwave oven for preventing the difficulty of inserting a coil that is caused due to a burr of resin formed during the molding of the coil.
It is yet another object to provide a transformer for a microwave oven which maintains a uniform thickness of resin while molding the resin on the coil.
It is still another object to provide a transformer for a microwave oven capable of adjusting the number of stacks of a magnetic path core even after the size of the core and the coil is determined.
It is still another object to provide a transformer for a microwave oven having a reduced manufacturing cost by omitting a process of varnish impregnation.
It is still another object of the present invention to provide a transformer for a microwave oven having a reduced manufacturing cost by omitting a process of welding the respective cores.
The above object is accomplished by a transformer for a microwave oven according to the present invention, including a first core having a coil inserting section having one open side; a plurality of coils sequentially inserted into the coil inserting section in the inter-electrically insulated state; a second core coupled to the first core, and for covering the open side of the coil inserting section; and a resin molding section formed to cover the whole area of the plurality of coils.
Here, the plurality of coils may be inter-electrically insulated by an insulating paper, or may be sequentially inserted into the auxiliary spacing portion in the inter-electrically insulated state and is then inserted into the coil inserting section together with the auxiliary spacing portion, or may be inserted into the coil inserting section together with the auxiliary spacing portion after being directly wound around the auxiliary spacing portion.
The auxiliary spacing portion is in mesh shape for enough contact of the resin with the plurality of coils, and the auxiliary spacing portion includes a plurality of projections formed on the outer surface thereof for a uniform thickness of the resin layer.
The resin molding section is preferably formed of a bulk molding compound resin, and the first and second cores may be automatic lamination cores in which a plurality of iron plates are made by simultaneous stamping and caulking processes. In such a case, it is preferable that both edges of the first core opposite from the second core are beveled.
Further, the above objects are accomplished by including a first core having a coil inserting section having one open side; a second coil, a heater coil, a magnetic path core, and a first coil sequentially inserted into the coil inserting section in the inter-electrically insulated state; a second core coupled to the first core for covering the open side of the coil inserting section; and a bulk molding compound resin molding section formed to cover the whole area of the second coil, the heater coil, and the first coil.
Further, the above objects are accomplished by including a first core having a coil inserting section having one open side; a second coil, a heater coil, a magnetic path core, and a first coil sequentially inserted into the auxiliary spacing portion after being inter-electrically insulated by the insulating paper, and then inserted into the coil inserting section together with the auxiliary spacing portion; a second core coupled to the first core for covering the open side of the coil inserting section; and a bulk molding compound resin molding section formed to cover the whole area of the second coil, the heater coil, and the first coil.
Further, the above objects are accomplished by including a first core having a coil inserting section having one open side; a second coil, a heater coil, a magnetic path core, and a first coil sequentially inserted into the auxiliary spacing portion in the inter-electrically insulated state, and then inserted into the coil inserting section together with the auxiliary spacing portion; a second core coupled to the first core for covering the open side of the coil inserting section; and a bulk molding compound resin molding section formed to cover the whole area of the second coil, the heater coil, and the first coil, where the second and first coils are formed of bulk molding compound resin, and the magnetic path core is wrapped by the insulting paper, so that the second coil, the heater coil, the magnetic path core, and the first coil are inter-electrically insulated with each other.
Further, the above objects are accomplished by including a first core having a coil inserting section having one open side; a second coil, a heater coil, a magnetic path core, and a first coil sequentially inserted into the auxiliary spacing portion after being inter-electrically insulated by the insulating paper, and then inserted into the coil inserting section together with the auxiliary spacing portion; a second core coupled to the first core for covering the open side of the coil inserting section; and a bulk molding compound resin molding section formed to cover the whole area of the second coil, the heater coil, and the first coil, where the second coil, the heater coil, and the first coil are directly wound around the auxiliary spacing portion.